Speaker
Description
GaAs based photocathodes play a crucial role as the primary source of polarized electron beams in various accelerator facilities, including CEBAF at Jefferson National Laboratory and the Electron Ion Collider (EIC) at Brookhaven National Laboratory in the USA. The electron pre-injector at the EIC requires a 1-2 nC bunch with at least 85% spin polarization from a superlattice GaAs photocathode, with longitudinal polarization subsequently rotated to transverse directions using a pair of Wien filters before injecting into the linac. To address the source requirements, we have carried out an extensive study of MOCVD-grown superlattice GaAs/GaAsP structures incorporating a Distributed Bragg Reflector (DBR) underneath. We have incorporated different surface cleaning and activation mechanisms to improve the QE and lifetime of the photocathodes. Besides, 2D protective coatings for polarized electron sources are being explored. In this paper, we will report our advances in electron source development.